KR101289615B1 - Integrated unit for electrical/reliability testing with improved thermal control - Google Patents

Abstract

According to one aspect of the invention, the heat-controllable integrated unit is configured to hold at least one device under test (DUT). The unitary unit comprises at least one heater board, which is made of a thermally conductive material and has at least one global heater configured to globally heat the DUT board. The DUT board of the unitary unit is in thermal contact with the at least one heater board, the DUT board comprising a plurality of sockets, each socket configured to hold at least one DUT. The DUT has a conductor path for conducting electrical signals between the DUT terminals in the socket and the test equipment. Each socket includes an associated temperature sensor and an individually controllable local heater, the local heater operating a local heater for each socket based on a temperature indication from the temperature sensor.

Description

Integrated unit for electrical reliability testing with improved thermal control {INTEGRATED UNIT FOR ELECTRICAL / RELIABILITY TESTING WITH IMPROVED THERMAL CONTROL}

Semiconductor reliability tests require accurate electrical stress and measurements under precise temperature control. Typical test temperatures range from slightly above room temperature to up to 350 ° C and are due to differences in spontaneous heat generation (Joule fever) between one Device Under Test (DUT) and the other DUT. Spatial temperature fluctuations get worse. Moreover, DUT sockets, printed circuit boards (DUT boards), and insulating materials readily available at temperatures below 250 ° C. are difficult to manufacture for high temperature applications.

In recent years, convection ovens have been used that are optimized for the required temperature range. However, these ovens have two drawbacks that limit their performance, the first being that when the oven requires a small number (5-15) of DUTs due to the large volume associated with the heating mechanism (hot air convection), It is impractical, and second, by definition, local temperature fluctuations and nonuniformity are often problematic because temperature control is global.

Another technique yielded a small oven unit integrated with a single DUT board (prior art: US Pat. No. 6,097,200), in which case the DUT under test is maintained at a controlled temperature within the required range. The concept is based on an electrically heated surface that transfers heat through a number of metal plates to a radiator located very close to the DUT. The unit is compact and does not contain air convection, but heating is done globally for the entire unit, with a single temperature sensor located on the DUT board. Another limitation is that the DUT board must change every time the pin assignment of the packaged DUT changes.

According to one aspect of the invention, the heat-controllable integrated unit is configured to hold at least one device under test (DUT). The unitary unit comprises at least one heater board, which is made of a thermally conductive material and has at least one global heater configured to globally heat the DUT board. The DUT board of the unitary unit is in thermal contact with the at least one heater board, the DUT board comprising a plurality of sockets, each socket configured to hold at least one DUT. The DUT has a conductor path for conducting electrical signals between the DUT terminals in the socket and the test equipment. Each socket includes an associated temperature sensor and an individually controllable local heater, the local heater operating a local heater for each socket based on a temperature indication from the temperature sensor.

1 is an exploded view of a DUT board assembly of one embodiment.
2 is an exploded view of a DUT board assembly, without a buffer board.
3 is a top perspective view of the DUT socket;
4 is a cross-sectional view of the DUT socket of FIG.
5 is a plan view of a socket bottom plate with a temperature sensor;
6 is an exploded view of a DUT socket and associated temperature sensor.

The inventors have realized a heating and integration technique in which a specially designed heater board on which a global heater and a local electric heater are printed can be integrated with the DUT board so that the DUT socket can be in direct physical contact with the local heater. In addition, a dedicated temperature sensor is physically integrated into each DUT socket. As a result, good temperature control is achieved for each DUT, regardless of the spatial and nonuniformity of the joule rows between one DUT and the other. Finally, the unit can include an easily accessible printed circuit board outside the heated area, and the necessary bonding can be manually "programmed" by plug-in jumpers, making it suitable for a wide range of bonding structures. do.

Referring now to FIG. 1, in one form, a main component called a “DUT board assembly” includes two identical heater boards, two identical buffer boards, a DUT board, and a socket. A perspective and exploded view of an example DUT board assembly is shown in FIG. 1. Each heater board (THB: Top Heater Board and BHB: Bottom Heater Board) can be made of metal, and a thin dielectric film is printed on the metal for insulation. The heating element is placed on top of the dielectric layer (by printing). Printed gold traces not only provide a solid, low-resistance connection to external stimuli, but also provide interconnections between heating elements, if desired. The buffer board may be made of an electrically insulating but thermally conductive material (eg, mica) and is located between the heater board and the DUT board to prevent excessive mechanical stress on the printed layer of the DUT board. . Such a buffer board has essentially no functional use and is therefore presented for reference only in FIG. 1. The following description is based on FIG. 2 which is similar to FIG. 1 except that there is no buffer board. In the embodiment shown, the assembly is "duplex". That is, the DUT is configured on both sides of the DUT board.

Referring now to FIG. 2, the upper heater board THB is mechanically attached to the top of the DUT board DUTB, and the lower heater board BHB is mechanically attached to the bottom of the DUT board. In connection with FIG. 2, "top" and "bottom" are optional. Because there is essentially no top or bottom, both sides are symmetrical structure and symmetrical layout. In FIG. 2, each heater board has a total of eight heating elements, but the number may vary from embodiment to embodiment. The four heating elements LH1, LH2, LH3, LH4 are "local". That is, each local heating element is located under a single socket. Global heating elements (GHL, GH) are located on the left and right sides of the heater board, respectively, thus heating the entire DUT board rather than one specific socket. The two remaining elements, the lower heater BH and the upper heater TH, are located at the bottom and top of the heater board, respectively. These heaters control the local temperature of the upper and lower sockets and compensate for heat losses at the upper and lower edges. All heating elements operate individually or turn off to the appropriate level and do not affect the condition of other heaters. As an example, independent control of the heating element is accomplished using spring-loaded pegs (“pogo pins”) to deliver electrical stimulation through the gold plated pads (PCS of FIG. 2).

In general, most of the heat can be transferred by a global heater, and local heaters are mainly used to fine tune the DUT temperature. Strong thermal coupling between the global heater and the DUT board, and between all DUT packages, their sockets and local heaters underneath, is attributed to accurate, stable and fast DUT temperature control.

3, 4, and 5 are used to detail the thermal action around the DUT. The particular socket shown in this application (see US Pat. No. 6,798,228) and the DUT package represent an example, and generally, any high temperature socket with integral temperature sensor in thermal contact with a local heating element may be used, Suitable DUT boards and heater boards can be fabricated to accommodate them.

In the example shown the DUT socket is made of two plates, namely the lower plate Sb and the upper plate St. The temperature sensor SENT is inserted into a groove in the bottom plate, the leads of which are connected by a conductive spring SPR and a receptacle PIN. Likewise, the terminals of the packaged DUT are inserted into the holes of the receptacle and top plate and contact the lower pad SPAD on the DUT board DUTB. Details regarding the spring action, mechanical attachment of the receptacle, and the advantages of this contact technique are already known (see US Pat. No. 6,798,228) and are not described in further detail.

The lower socket plate Sb is formed to swell the region of the receptacle pin, and is fitted with the cut portion CUTO of the heater board THB or BHB. The central portion of Sb with the temperature sensor is in actual contact with the associated local heater of the heater board. The socket, local heating element, temperature sensor, DUT package, DUT board form a tightly coupled precision assembly with efficient thermal, electrical, and mechanical features, as shown in FIG. 6.

At the start of a typical high temperature test, the temperatures of all individual sensors are read by a dedicated, microcontroller based unit. In most cases, this temperature is much lower than the intended test temperature, so all heaters are turned on. The control unit continuously reads the temperature and dynamically turns on and off the various heaters based on a temperature control algorithm, commonly referred to as Proportional-Integral-Derivative (PID). The unique combination of "global" heaters and socket-specific ("local") heaters provides accurate, responsive, and energy efficient temperature control for each package tested.

Thus, it can be seen that by using global and local electric heaters, excellent temperature control can be provided for each DUT, regardless of the spatial non-uniformity and difference in Joule heating between the DUTs.

Moreover, the design can be implemented to provide connection personalization. In general, a DUT is bonded to a package in a manner unique to the DUT. For example, in one typical 20-pin package, pin 1 can be connected to current force (+), pin 5 can be connected to current sink (-), and pin 11 and pin 17 can be associated sense pins. . However, different 20-pin DUTs can have the same pins configured in different ways to connect to the same signal. In some examples, a peg or jumper may be provided to reconfigure in such a way that the pins are connected to the tester signal, such that the same hardware (eg, socket) may be used for the various hardware structures.

Claims (10)

A heat-controllable integrated unit, configured to hold at least one device under test (DUT),
At least one heater board, composed of a thermally conductive material, configured to globally heat the DUT board, and having at least one global heater,
A DUT board in thermal contact with the at least one heater board, the DUT board comprising a plurality of sockets, each socket configured to hold at least one DUT, the DUT board being tested with the DUT terminals in the socket Having a conductor path for conducting electrical signals between the equipment, each socket includes an associated temperature sensor and an individually controllable local heater, which local heater is based on a temperature indication from the temperature sensor. And operate the local heater for heating the at least one DUT in each socket.
Wherein the global heater is printed on at least one heater board, the local heater being a printed heating element
Integrated unit, heat-controlled. The method of claim 1,
The at least one heater board is two heater boards,
The DUT board is located between the two heater boards
Integrated unit, heat-controlled. 3. The method according to claim 1 or 2,
A buffer board composed of an electrically insulating but thermally conductive material and positioned between the at least one heater board and the DUT board, the buffer board providing mechanical support to the DUT board to provide excessive mechanical stress on the printed layer of the DUT board. Prevent the buffer board
The heat-controllable integrated unit further comprising. 3. The method according to claim 1 or 2,
The temperature sensor associated with each DUT socket is located in a groove associated with the DUT socket, wherein each lead of the temperature sensor is connected to an electrical path on at least one heater board through a spring, the lead being connected by a pin. Forced against spring
Integrated unit, heat-controlled. 3. The method according to claim 1 or 2,
At least some of a global heater and a local heater are each connected to an electrical path on the at least one heater board, the electrical path being a path to an external connector capable of controlling heater start and stop.
Integrated unit, heat-controlled. 3. The method according to claim 1 or 2,
At least some of a global heater and a local heater are each connected to an electrical path on the at least one heater board, the electrical path being a path to a pin contact with a spring-loaded peg inserted therein, The pin contacts provide an external connection that can control the heater starting and stopping.
Integrated unit, heat-controlled. 3. The method according to claim 1 or 2,
Reconfigurable conductor paths for conducting electrical signals between DUT terminals in the socket and test equipment
Integrated unit, heat-controlled. The method of claim 7, wherein
The reconfigurable conductor path includes a peg or jumper provided to reconfigure how the pins of the DUT in the socket are connected to the tester signal.
Integrated unit, heat-controlled. In the heater control method of the unitary unit is configured to hold at least one device under test (DUT), The unitary unit,
At least one heater board composed of a thermally conductive material and having at least one global heater configured to globally heat the DUT board,
A DUT board in thermal contact with the at least one heater board, the DUT board comprising a plurality of sockets, each socket configured to hold at least one DUT, the DUT board being tested with the DUT terminals in the socket Having a conductor path for conducting electrical signals between the equipment, each socket includes an associated temperature sensor and an individually controllable local heater, which local heater is based on a temperature indication from the temperature sensor. And operate the local heater for heating the DUT in each socket.
The method comprising:
Controlling the at least one global heater to globally heat the DUT board;
Receiving a signal from the temperature sensor and selectively operating a local heater based on the signal to maintain a desired temperature in each socket
Wherein the global heater is printed on at least one heater board, the local heater being a printed heating element
Heater control method of integrated unit. The method of claim 9,
Selectively operating the local heater includes processing the received temperature sensor signal in accordance with a Proportional-Intergral-Derivative (PID) algorithm.
Heater control method of integrated unit.

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